CN103759642A - Two-dimensional microscale measuring device and method based on three-core fiber bragg grating - Google Patents

Abstract

The invention belongs to the technical field of precision instrument manufacture and measurement and provides a two-dimensional microscale measuring device and method based on a three-core fiber bragg grating. The device comprises a wideband light source, a spectrum analyzer, an optical circulator, a control computer, a multiplex photoswitch and an external reference grating. The multiplex photoswitch is communicated with a three-core optical fiber fan-out device through three single mode optical fibers respectively. One end of the three-core optical fiber is connected to the three-core optical fiber fan-out device, a three-core fiber bragg grating probe is fixedly arranged at the other end of a three-core fiber through a probe clamping device, and the three-core fiber and the three-core fiber bragg grating probe are connected to form a channel. The method comprises the following steps that the control computer controls the multipath photoswitch to switch optical paths, the spectrum analyzer is utilized to respectively measure reflectance spectrums of the fiber bragg grating, and two-dimensional microscale measurement of non-temperature coupling is achieved by utilizing the differential data processing algorithm. The two-dimensional microscale measuring device has the advantages of being high in precision, small in contact force and not influenced by the shadowing effect. In addition, the service life of the probe is long.

Description

Two-dimensional micro-scale measurement device and method based on three-core fiber grating

technical field

The invention belongs to the technical field of precision instrument manufacturing and measurement, and in particular relates to a two-dimensional micro-scale measurement device and method based on a three-core optical fiber grating.

Background technique

With the continuous development of the aerospace industry, automobile industry, electronics industry and cutting-edge industries, the demand for precision and tiny components has increased dramatically. Due to the limitations of the space scale and the shadowing effect of the tiny components to be measured, as well as the influence of the measurement contact force, it is difficult to realize the precise measurement of the scale of the tiny components, especially the difficulty of improving the depth of the measurement of the tiny inner cavity components, which has become a constraint to the development of the industry. "bottleneck". In order to achieve smaller size measurement and increase the measurement depth, the most widely used method is to use a slender probe to penetrate into the inner cavity of tiny components for detection, and measure the tiny inner dimensions at different depths by aiming at the signal. Therefore, at present, the precise measurement of the size of tiny components is mainly based on the coordinate measuring machine combined with the aiming and sending detection system with a slender probe. Since the development of the coordinate measuring machine technology has been relatively mature, it can provide precise three-dimensional space movement, so the aiming The detection method of the trigger probe becomes the key to the design of the detection system for small component sizes.

At present, the main means of measuring the size of tiny components include the following methods:

1. Professor Tan Jiubin and Professor Cui Jiwen of Harbin Institute of Technology in China proposed a probe structure based on dual optical fiber coupling. The two optical fibers are connected through the fusion ball at the end, and the fusion ball is used as the probe, and a longer optical fiber is introduced into the light. A short lead-out light overcomes the limitation of measuring depth by microbead scattering method, and can realize accurate aiming when measuring micro-deep holes with a diameter not less than 0.01mm and a depth-to-diameter ratio not greater than 15:1. Although this method overcomes the shadowing effect to a certain extent, the light energy of the reverse transmission achieved by the coupling sphere is very limited, and it is difficult to further improve the measurement depth.

2. The National Institute of Standards and Technology of the United States uses a probe with a single optical fiber measuring rod combined with a micro-optical bead. Through optical design, the imaging of the optical fiber measuring rod is magnified by about 35 times in the two-dimensional direction, and two area array CCDs are used to distinguish and receive the two-dimensional The image formed by the optical fiber measuring rod in the direction, and then the contour detection is performed on the received image, so as to monitor the tiny movement of the optical fiber measuring rod during the measurement process, and then realize the trigger measurement. The theoretical resolution of the detection system can reach 4nm , the probe diameter of the detection system is Φ75μm. In the experiment, the aperture of Φ129μm was measured, and the probability value of the expanded uncertainty reached 70nm (k=2), and the measurement force was in the order of μN. This method has high detection resolution and high measurement accuracy, and the probe used is easy to miniaturize, and can measure micropores with a large depth-to-diameter ratio. However, this method must use two sets of imaging systems to detect the two-dimensional touch displacement of the optical fiber measuring rod, resulting in a complex system structure and a relatively large amount of calculation of measurement data. These factors lead to poor real-time performance of the detection system and a relatively complex system composition.

3. The Swiss Joint Metrology Office has developed a new type of coordinate measuring machine dedicated to the traceable measurement of small structural parts with nanometer precision. The measuring machine adopts a new type of contact probe with a bending hinge structure based on the principle of parallel kinematics. This design can reduce the moving mass and ensure low stiffness in all directions. It is a probe with three-dimensional space structure detection capability. This sensing structure has a measuring force below 0.5mN and supports replaceable probes with diameters as small as Φ100μm. The detection system incorporates a high position accuracy platform developed by Philips CFT with a position accuracy of 20nm. The standard deviation of the measurement repeatability of the measurement system reaches 5nm, and the uncertainty of the measurement result is 50nm. The structural design of this method is complex, and the measuring rod is required to have high rigidity and hardness, otherwise it is difficult to realize effective touch displacement sensing, which makes it difficult to further miniaturize the measuring rod structure, and the depth-to-diameter ratio of the measurement is also restricted. The resolution of the system is difficult to further improve.

4. Professor Cui Jiwen and Yang Fuling of Harbin Institute of Technology in China proposed a micropore size measurement device and method based on FBG Bending. This method uses the probe processed by fiber grating and the corresponding light source and detection device as the aiming trigger system. The dual-frequency laser interferometer length measurement device can obtain the micropore size of different sections. When the micro-scale sensor of this method touches the deformation, the main stress of the probe does not act on the fiber grating, and the resolution of the system is very low, which is difficult to further improve.

In summary, in the current micro-size and coordinate detection methods, probes made of optical fibers have attracted widespread attention due to their small probe size, small measurement contact force, large measurement depth-to-diameter ratio, and high measurement accuracy. Its unique optical and mechanical properties realize the precise measurement of tiny dimensions at a certain depth through various methods. The main problems of existing measurement methods are:

1. It is difficult to further improve the touch displacement resolution of the detection system. The primary magnification of the existing detection system is low, resulting in a low overall magnification, and it is difficult to further improve the resolution of the touch displacement. The FBG probe based on FBG Bending's micropore size measurement method cannot apply the main micro-touch displacement effect on the FBG, and the sensing signal converted into spectral information is weak, and the resolution of the system is very low.

2. The real-time performance of the detection system is poor, and it is difficult to realize precise online measurement. The detection method adopted by the National Institute of Standards and Technology must use a two-way area array CCD to receive signal images, and a more complex image algorithm must be used to achieve high-resolution monitoring of the displacement of the optical fiber measuring rod, which results in a large amount of data that the measurement system needs to process. The amount is greatly increased, which reduces the real-time performance of the detection system, and it is difficult to realize the synchronization between the small inner cavity size and the synchronization of the aiming signal and the start and stop measurement in the process of two-dimensional coordinate measurement.

3. There is coupling of two-dimensional radial touch displacement. The probe of the micropore size measurement method based on FBG Bending has the same performance in all directions, and there is coupling in the radial two-dimensional touch displacement sensing, and it cannot be separated, resulting in a large error in the two-dimensional measurement, and the radial two-dimensional measurement cannot be realized. Accurate measurement of touch displacement.

4. Does not have the decoupling capability of radial and axial detection. The detection methods mentioned above either do not have the ability to detect axially or do not have the ability to decouple radial and axial detection. When performing micro-scale measurements, the measurement steps are complicated and the measurement efficiency is low.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of low resolution and single dimension of the measurement method for tiny components in the prior art, and provide a device and method suitable for two-dimensional micro-scale measurement of tiny components. The three-core fiber grating probe is used in After the end is affected by the touch displacement, the stress causes the parameters of the fiber Bragg grating to change, and then the central wavelength of the reflection spectrum changes accordingly. A multi-channel optical switch is used to switch the channels for measuring the fiber Bragg grating to obtain the corresponding central wavelength information of the reflection spectrum and then The differential data processing reduces the impact of temperature fluctuations on the measurement results and greatly improves the device's ability to adapt to the environment, thereby realizing a new two-dimensional micro-scale measurement without coupling of temperature.

The technical solution of the present invention is: a two-dimensional micro-scale measurement device based on a three-core fiber grating, including a broadband light source, a spectrum analyzer, an optical ring device, a control computer, a multi-channel optical switch and an external reference grating, the broadband light source The optical circulator and the optical circulator are respectively connected with the multi-channel optical switch, the multi-channel optical switch and the control computer, the control computer and the spectrum analyzer, the multi-channel optical switch and the external reference grating to form a path, and the three single-mode The optical fiber connects the multi-channel optical switch with the three-core optical fiber fan-out respectively, one end of the three-core optical fiber is connected to the three-core optical fiber fan-out, and the other end of the three-core optical fiber is fixed to the three-core optical fiber through the probe holder. A fiber grating probe, the three-core optical fiber is connected with the three-core fiber grating probe to form a path.

A two-dimensional micro-scale measurement method based on three-core fiber gratings is as follows: during the measurement process, the multi-channel optical switch switches different optical paths under the control of the control computer, and uses a spectrum analyzer to measure the three cores inside the three-core fiber grating probe. Reflection spectra of fiber gratings and external reference gratings. During data processing, differential data processing is performed on the center wavelengths of the two fiber grating reflection spectra outside the inner center of the three-core fiber grating probe, which can be decoupled along the distribution direction of the three-core fiber cores. The one-dimensional radial touching displacement and temperature drift of the three-core fiber Bragg grating probe are processed by differential data processing between the central wavelength of the fiber grating reflection spectrum at the center of the three-core fiber grating probe and the central wavelength of the external reference grating reflection spectrum, and no radial touching displacement and temperature drift are obtained. Coupled axial touch displacement to realize two-dimensional micro-scale measurement without temperature coupling.

The advantages of the present invention are:

1. The two-dimensional micro-scale measurement device and method based on three-core fiber gratings have the characteristics of high precision, small contact force, no damage to the surface of the measured component, and long service life of the probe.

2. The optical detection signal instrument is transmitted inside the fiber grating, which converts the contact in space into the change of the central wavelength of the reflection spectrum. When measuring micro-scale components, it is not affected by the shadowing effect of components. The measurement depth-to-diameter ratio can reach 100:1, which meets The requirements for micro-scale measurement of microstructures with large aspect ratio are fulfilled.

3. The two-dimensional micro-scale measurement method based on the three-core fiber grating can realize the coupling-free radial and axial measurements at the same time, which simplifies the steps of micro-scale measurement and improves the efficiency of micro-scale measurement.

4. A cross-reference differential compensation system is designed inside the probe, combined with a two-dimensional micro-scale measurement method based on a three-core fiber grating, which eliminates the impact of ambient temperature changes on the measurement and greatly improves the adaptability of the sensor to the environment. It can go deep into the space and environment where traditional measurement tools cannot work normally for precise measurement, such as narrow semi-enclosed spaces and flammable and explosive environments, and is also suitable for industrial on-site measurement.

Description of drawings

Figure 1 is a schematic diagram of the structure of a two-dimensional micro-scale measurement device based on a three-core fiber grating;

Fig. 2 is A-A sectional view among Fig. 1;

Fig. 3 is the enlarged view of the section of the three-core fiber grating probe in Fig. 1;

In the figure: 1. Broadband light source, 2. Spectrum analyzer, 3. Optical circulator, 4. Control computer, 5. Multi-channel optical switch, 6. Single-mode optical fiber, 7. External reference grating, 8. Three-core optical fiber fan Output device, 9. Three-core optical fiber, 10. Probe holder, 11. Three-core fiber grating probe.

Detailed ways

Below in conjunction with accompanying drawing, specific embodiment of the present invention is described in further detail:

A two-dimensional micro-scale measurement device based on a three-core fiber grating, including a broadband light source 1, a spectrum analyzer 2, an optical ring device 3, a control computer 4, a multi-channel optical switch 5 and an external reference grating 7, the broadband light source 1 The optical circulator 3 is connected to the multi-channel optical switch 5, the multi-channel optical switch 5 is connected to the control computer 4, the control computer 4 is connected to the spectrum analyzer 2, and the multi-channel optical switch 5 is connected to the external The reference grating 7 is connected to form a path, and the three single-mode optical fibers 6 respectively connect the multi-channel optical switch 5 with the three-core optical fiber fan-out device 8, and one end of the three-core optical fiber 9 is connected to the three-core optical fiber fan-out device 8. The other end of 9 is fixed with a three-core fiber grating probe 11 through a probe holder 10, and the three-core fiber 9 is connected with the three-core fiber grating probe 11 to form a passage.

A two-dimensional micro-scale measurement method based on three-core fiber gratings is as follows: during the measurement process, the multi-channel optical switch 5 switches different optical paths under the control of the control computer 4, and uses the spectrum analyzer 2 to measure the three-core fiber grating probes respectively The reflection spectra of the three fiber gratings inside 11 and the external reference grating 7, during data processing, the differential data processing is performed on the central wavelength of the reflection spectra of the two fiber gratings outside the inner center of the three-core fiber grating probe 11, which can be decoupled along the three cores For the one-dimensional radial displacement and temperature drift in the distribution direction of the fiber core, differential data processing is performed on the center wavelength of the reflection spectrum of the fiber grating at the center of the three-core fiber grating probe 11 and the center wavelength of the reflection spectrum of the external reference grating 7, and no Radial contact displacement and axial contact displacement coupled with temperature drift realize two-dimensional micro-scale measurement without temperature coupling.

Working process of the present invention is as follows:

The broadband light generated by the broadband light source 1 enters the multi-channel optical switch 5 through the optical circulator 3, and the multi-channel optical switch 5 is under the control of the control computer 4, and the spectrum analyzer 2 respectively measures the three fiber gratings in the three-core fiber grating probe 11 and the central wavelength of the reflection spectrum of the external reference grating 7. When the three-core fiber grating probe 11 touches the component to be tested, the center wavelength of the reflection spectrum of the fiber grating in the three-core fiber grating probe 11 will change. Differential data processing is performed on the central wavelengths of the reflection spectra of the two gratings outside the center of the three-core fiber grating probe 11, and the temperature-decoupled radial touch displacement along the core distribution direction of the three-core fiber can be obtained; for the three-core fiber The grating at the center of the grating probe 11 and the central wavelength of the reflection spectrum of the external reference grating 7 are differentially processed to obtain an axial touch displacement without radial touch displacement and temperature drift coupling.

The two-dimensional micro-scale measurement of the component to be tested is finally realized by integrating the radial and axial contact displacement information.

Claims (2)

1. A two-dimensional micro-scale measurement device based on a three-core fiber grating, including a broadband light source (1), a spectrum analyzer (2), an optical ring device (3), a control computer (4), and a multi-channel optical switch (5 ) and an external reference grating (7), the broadband light source (1) and the spectrum analyzer (2) are respectively connected with the optical circulator (3), the optical circulator (3) is connected with the multi-channel optical switch (5), the multi-channel The optical switch (5) is connected with the control computer (4), the control computer (4) and the spectrum analyzer (2), and the multi-channel optical switch (5) is connected with the external reference grating (7) to form a path, which is characterized in that three single-mode optical fibers (6) The multi-channel optical switch (5) is communicated with the three-core optical fiber fan-out device (8) respectively, and one end of the three-core optical fiber (9) is connected on the three-core optical fiber fan-out device (8), and the three-core optical fiber ( The other end of 9) is fixed with a three-core fiber grating probe (11) through a probe holder (10), and the three-core fiber (9) is connected with the three-core fiber grating probe (11) to form a passage . 2. A two-dimensional micro-scale measurement method based on a three-core fiber grating, characterized in that in the measurement process, a multi-channel optical switch (5) switches different optical paths under the control of a control computer (4), using a spectrum analyzer ( 2) Measure the reflection spectra of the three fiber gratings inside the three-core fiber grating probe (11) and the external reference grating (7) respectively. During data processing, two optical fibers outside the center of the three-core fiber grating probe (11) The central wavelength of the grating reflection spectrum is used for differential data processing, which can decouple the one-dimensional radial touch displacement and temperature drift along the distribution direction of the three-core fiber core, and the reflection spectrum of the fiber grating at the center of the three-core fiber grating probe (11) The central wavelength and the central wavelength of the reflection spectrum of the external reference grating (7) are subjected to differential data processing to obtain axial touch displacement without radial touch displacement and temperature drift coupling, and realize two-dimensional micro-scale measurement without temperature coupling.

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